Research On The Dust Contribution And Control At Transfer Site In Cement Packing Plant

Being one of the major sources of atmospheric dust in our country, the annual dust emission raised by the cement industry accounts for about 40% the country's industrial dust emission a year. As the state has more and more strictly regulated the dust emissions from the cement industry with consistent efforts, the production and dust removal technology in the cement industry has gained substantial progress. The application of dust control technology so far, however, mainly focuses on raw material preparation, clinker burning and cement packaging,with less attention paid to cement transportation, especially to the dust generated at dust reproducing points.A cement packing plant in Xi'an is taken as the study site of the thesis. Dust distribution field, the characteristics of dust producing sources and the environment parameters in the workshop are analyzed to set up a reasonably simplified physical model. Computational fluid dynamics software FLUENT is used to simulate dust movement and distribution. It is found that dust concentrations around the transfer site exceed the standard limitation for the workspace. The simulation results fit the measured values nicely, thus the reliability of the model is verified.By scrutinizing the simulation results, it is found that the main reason of the unexpectedly high concentrations of dust lies in an undesirable pattern of air flow distribution and mobility of the dust producing source. In the current study with the existing dedusting system maintained, the model of semi-closed workshop is replaced by a closed shop model, and two kinds of air flow arrangement are established to simulate the flow field and the relevant dust concentration distribution in the shop in order to judge the respective effectiveness of dust control. The results show that the dust level with air outlets on the same side of the transfer conveyor is better than the one with the outlets on the opposite side of the conveyor. When the outlets are on the same side of the transfer conveyor, it can not only dilute the local dust, but can also discharge most of the dust outside. While the outlets are on the opposite side, only the dilution effect can be observed. In addition, calculations are performed to simulate the cases for outlets on the same side with different air speeds and outlet locations, leading to the best air velocity and vent locations for the optimum dust control, i.e the air speed of 2m/s-2.5m/s and the location of air vents below the height of the conveyor belt. This study reveals that the transformation of a semi-closed workshop into a closed one with a combined usage of overall ventilation and specific ventilation can effectively resolve the dust problem at dust reproducing locations in the cement packing plant and improve working environment.